Key figures in new cabinet

"I can say categorically that in my government, there won't be any form of pact or agreement with organised crime," he told the BBC. "It's not the path nor the route to greater security for the Mexican people."

Earlier this month, he denied the PRI's return to power would be a return to the past. "It is not, because this is a different country," he said.

The new president has indicated he will focus on tackling extortion, kidnapping and murder, and he has drafted in support from Colombia's former top policeman.

The outgoing president is due to take up a position at Harvard University and maintains he has made Mexico safer.

But for many Mexicans, Mr Calderon's legacy as president is of an estimated 10,000 drug-related killings a year for the past six years.